JPWO2015152092A1 - Nonaqueous electrolyte secondary battery negative electrode material, negative electrode mixture for nonaqueous electrolyte secondary battery, negative electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery, and vehicle - Google Patents

Abstract

To provide a negative electrode material for a non-aqueous electrolyte secondary battery having a high discharge capacity per volume and excellent cycle characteristics. The negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is a negative electrode material for a non-aqueous electrolyte secondary battery containing a non-graphitic carbon material and a carbon material mixture containing a graphite material as an active material, the non-graphite The carbonaceous material has an atomic ratio (H / C) of hydrogen atoms to carbon atoms of 0.10 or less by elemental analysis, an average particle diameter (Dv50) of 1 to 8 μm, and the graphitic material is a butanol method. The true density (ρBt) determined by the above is 2.15 g / cm 3 or more. The non-graphitic carbon material preferably has a true density (ρBt) of 1.52 g / cm 3 or more and less than 2.15 g / cm 3.

Description

  The present invention relates to a negative electrode material for a nonaqueous electrolyte secondary battery, a negative electrode mixture for a nonaqueous electrolyte secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a vehicle.

In recent years, non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) have been combined with a combination of an electric vehicle (EV) driven only by a motor or an internal combustion engine and a motor, taking advantage of the small size and light weight. It is expected to spread in automotive applications such as plug-in hybrid electric vehicles (PHEV) and hybrid electric vehicles (HEV). In particular, EV lithium-ion secondary batteries have improved energy density to extend the cruising range in a single charge, and improved battery input characteristics necessary to improve energy regeneration efficiency to further improve vehicle fuel efficiency. Is needed. Furthermore, since there is a high need to reduce the space on the battery, there is a need for improvement in energy density per volume and input characteristics.
In this automobile application, not the usage of repeating full charge and complete discharge like a small portable device, but the usage of repeating charging and discharging with a large current is made. In such a usage mode, the input and output are repeated while keeping the battery in a region where the input characteristics and the output characteristics are balanced, that is, when the full charge is 100%, about 50% of the charge range. May take form. Therefore, the input characteristics are improved by using a negative electrode material having a large potential change with respect to the capacity change under the use condition, instead of the negative electrode material exhibiting a substantially constant potential with respect to the capacity change under the use condition. be able to.

At present, carbon materials are used for negative electrode materials of lithium ion secondary batteries, and graphite materials and non-graphitizable carbon materials with low crystallinity are used (Patent Documents 1 and 2). The graphite material has a developed crystal structure and a high true density, so that it is easy to improve the electrode density, and it is suitable for a secondary battery for automobile use for the purpose of improving the energy density.
However, since the expansion and contraction in the c-axis direction accompanying charge / discharge is large, it is difficult to obtain good charge / discharge cycle performance.
On the other hand, non-graphitizable carbon materials such as non-graphitizable carbon materials or easily graphitizable carbon materials have a gradual change in charge / discharge curves and superior input / output characteristics compared to graphitic materials. It is suitable for secondary batteries for automobiles for the purpose of improvement. In addition, the non-graphitizable carbon material is excellent in charge / discharge cycle characteristics because the volume expansion and contraction associated with the storage and release of Li ions is small. However, non-graphitic carbon materials are disadvantageous in terms of increase in capacity per volume because of their low true density, and there is a problem that capacity deterioration tends to occur during high-temperature storage.
In-vehicle lithium-ion batteries are exposed to high temperatures in the summer, so charging and discharging cycles at high temperatures are also more important than secondary batteries for portable devices. Since the reaction with the liquid and the reaction between the carbon surface and the electrolytic solution are promoted, the improvement of the high temperature cycle and the characteristics after the high temperature cycle have become major issues.

JP-A-8-64207 International Publication No. 2005/098998

An object of the present invention is to provide a negative electrode material for a non-aqueous electrolyte secondary battery having a high energy density per volume and excellent cycle characteristics, a negative electrode mixture for a non-aqueous electrolyte secondary battery, a negative electrode for a non-aqueous electrolyte secondary battery, and It is providing a nonaqueous electrolyte secondary battery and a vehicle provided with the negative electrode for water electrolyte secondary batteries.
Another object of the present invention is to provide a non-aqueous electrolyte secondary battery negative electrode material having a high energy density per volume and excellent input / output characteristics, a non-aqueous electrolyte secondary battery negative electrode mixture, and a non-aqueous electrolyte secondary battery negative electrode. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery and a vehicle including the negative electrode for the non-aqueous electrolyte secondary battery.

In a negative electrode material for a non-aqueous electrolyte secondary battery including a non-graphitic carbon material and a carbon material mixture containing a graphite material as an active material, the true density (ρ _Bt ) determined by the butanol method is 1.52 g / cm ³ or more 1.70 g / cm ³ , the atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.10 or less, the average particle diameter (D _v50 ) is 1 to ₈ μm, and the graphite The material is a carbon for non-aqueous electrolyte secondary battery negative electrodes that is improved in both energy density per volume and cycle characteristics by using a carbon material mixture having a true density (ρ _Bt ) of 2.15 g / cm ³ or more. We have found that quality materials are provided.
In addition, in a negative electrode material for a non-aqueous electrolyte secondary battery including a non-graphitic carbon material and a carbon material mixture containing a graphite material as an active material, the true density (ρ _Bt ) obtained by the butanol method is 1.70 g / cm. ³ and less than 2.15 g / cm ³ , the atomic ratio of hydrogen atoms to carbon atoms (H / C) by elemental analysis is 0.10 or less, and the average particle diameter (D _v50 ) is 1 to ₈ μm For the non-aqueous electrolyte secondary battery negative electrode, the graphite material is improved in both input characteristics and cycle characteristics by using a carbon material mixture having a true density (ρ _Bt ) of 2.15 g / cm ³ or more. It has been found that a carbonaceous material is provided.
Specifically, the present invention provides the following.

(1) A negative electrode material for a non-aqueous electrolyte secondary battery including a non-graphitic carbon material and a carbon material mixture containing a graphite material as an active material, wherein the non-graphitic carbon material includes hydrogen atoms obtained by elemental analysis. The atomic ratio (H / C) of carbon atoms is 0.10 or less, the average particle diameter (D _v50 ) is 1 to ₈ μm, and the graphite material has a true density (ρ _Bt ) determined by a butanol method. 2. A negative electrode material for a non-aqueous electrolyte secondary battery, which is at least 15 g / cm ³ .

(2) The non-aqueous electrolyte 2 according to (1), wherein the non-graphitic carbon material has a true density (ρBt) determined by a butanol method of 1.52 g / cm ³ or more and 1.70 g / cm ³ or less. Negative electrode material for secondary batteries.

(3) the non-graphitic carbon material, true density determined by butanol method (RoBt) is greater 2.15 g / cm less than ³ from 1.70 g / cm ^3, a non-aqueous electrolyte according to the above (1) Negative electrode material for secondary batteries.

(4) The ratio of the average particle diameter (D _v50 ) of the non-graphitic carbon material to the average particle diameter (D _v50 ) of the graphite material is 1.5 times or more, and the above (1) to (3) The negative electrode material for nonaqueous electrolyte secondary batteries in any one.

(5) the non-graphitic carbon _{material, (D v90 -D v10) /} D v50 is 1.4 to 3.0, (1) to (4) a non-aqueous electrolyte according to any one of the two Negative electrode material for secondary batteries.

  (6) The negative electrode material for a nonaqueous electrolyte secondary battery according to any one of (1) to (5), wherein the carbon material mixture includes 20 to 80% by mass of the non-graphitic carbon material.

  (7) A negative electrode mixture for a non-aqueous electrolyte secondary battery, including the negative electrode material according to any one of (1) to (6) above, and further including a binder and a solvent.

  (8) The negative electrode mixture for a nonaqueous electrolyte secondary battery according to (7) above, comprising a water-soluble polymer binder and water.

  (9) A negative electrode for a non-aqueous electrolyte secondary battery obtained by the negative electrode mixture according to (7) or (8).

  (10) A nonaqueous electrolyte secondary battery comprising the negative electrode, the positive electrode, and an electrolytic solution according to (9) above.

  (11) A vehicle equipped with the nonaqueous electrolyte secondary battery according to (10).

According to the present invention, by using a carbon material mixture containing a specific non-graphitic carbon material and a graphite material as an active material, the discharge capacity per volume increases, and the negative electrode containing the non-graphitic carbon material alone Provided is a negative electrode material for a non-aqueous electrolyte secondary battery that has a higher energy density per volume than that of the material and maintains cycle characteristics.
In addition, according to the present invention, by using a carbon material mixture containing a specific non-graphitic carbon material and a graphite material as an active material, input / output characteristics are improved, and the non-graphitic carbon material is contained alone. Provided is a negative electrode material for a non-aqueous electrolyte secondary battery that has a higher energy density per volume than the negative electrode material.

  Hereinafter, embodiments of the present invention will be described.

[1] Negative electrode material for non-aqueous electrolyte secondary battery The negative electrode material for non-aqueous electrolyte secondary battery of the present invention includes a non-graphite carbon material and a carbon material mixture containing a graphite material as an active material. The negative electrode material for a secondary battery, wherein the non-graphitic carbon material has an atomic ratio (H / C) of hydrogen atom to carbon atom of 0.10 or less by elemental analysis, and an average particle diameter (D _v50 ) of 1 The graphite material is characterized in that the true density (ρ _Bt ) determined by the butanol method is 2.15 g / cm ³ or more.

(True density)
The carbon material mixture in the present invention is a mixture of a non-graphitic carbon material and a graphite material. The non-graphitic carbon material has a true density (ρ _Bt ) determined by a butanol method of 1.52 g / cm ³ or more and less than 2.15 g / cm ³ , and the graphitic material has a true density (ρ _Bt ) of 2 .15 g / cm ³ or more.

The non-graphitic carbon material preferably has a true density (ρ _Bt ) determined by a butanol method of 1.52 g / cm ³ or more and less than 1.70 g / cm ³ . As a result, the negative electrode material for a non-aqueous electrolyte secondary battery containing the carbon mixture can secure the discharge capacity necessary for the automobile battery while maintaining the characteristic that the potential gradually changes with respect to the discharge capacity. In particular, in a practical state used in a charging range of around 50%, a high discharge capacity per volume can be exhibited while maintaining the potential difference between the negative electrode and the positive electrode.

If the true density (ρ _Bt ) of the non-graphitic carbon material in the carbon mixture is less than 1.52 g / cm ³ , the energy density that can be stored is small, so the volume of the electrode must be increased to ensure battery capacity. No. If it exceeds 1.70 g / cm ³ , the average interplanar spacing d ₀₀₂ of the carbonaceous material becomes relatively small, and the expansion and contraction of the carbonaceous material becomes large, so the tendency of capacity reduction associated with the charge / discharge cycle increases. Therefore, the true density of the non-graphitic carbon material is preferably 1.52 g / cm ³ or more and 1.70 g / cm ³ or less. The upper limit is preferably 1.68 g / cm ³ or less, more preferably 1.65 g / cm ³ or less. The lower limit is preferably 1.53 g / cm ³ or more, more preferably 1.55 g / cm ³ or more.

Non-graphitic carbon material, true density determined by butanol method ([rho _Bt) is preferably larger 2.15 g / cm less than ³ from 1.70 g / cm ^3. As a result, the negative electrode material for a non-aqueous electrolyte secondary battery containing the carbon mixture can secure the energy density necessary for the automobile battery while maintaining the characteristic that the potential gradually changes with respect to the discharge capacity. In particular, in a practical state used in a charging region of around 50%, high input / output characteristics can be exhibited while maintaining the potential difference between the negative electrode and the positive electrode.

If the true density (ρ _Bt ) of the non-graphitic carbon material in the carbon mixture is 1.70 g / cm ³ or less, the energy density that can be stored is small, so to secure battery capacity, the volume of the electrode must be increased. No. When it is at least 2.15 g / cm ³ , there is no region where the potential gradually changes in the charge / discharge curve, and the input / output characteristics are degraded. Therefore, the true density of the non-graphitic carbon material is less than 1.70 g / cm ³ greater than 2.15 g / cm ³ are preferred. The lower limit is more preferably 1.75 g / cm ³ or more, and the upper limit is more preferably 2.10 g / cm ³ or less.

The true density (ρ _Bt ) of the graphite material in the carbon mixture is preferably 2.15 g / cm ³ or more because a high energy density per volume is obtained and the charge / discharge efficiency is also increased.

True density ([rho _Bt) of carbon material mixture in the present invention, 1.65 g / cm ³ or more 2.15 g / cm ³ or less. The true density (ρ _Bt ) is obtained by a predetermined measurement method. In addition, since an additivity rule corresponding to the mixing ratio of the non-graphitic carbon material and the graphite material to be mixed is established, the true density of the mixed non-graphitic carbon material and the graphite material is used to determine the carbon material mixture. The true density can also be calculated.

The carbon material mixture in the present invention is separated by utilizing the difference in density, and can be specified by the type, particle diameter, and structure of the non-graphitic carbon material and the graphitic material contained. For example, the operation can be performed in accordance with the density pipe method of the carbon fiber-density test method (JIS R7603-1999) to identify it. In addition, true density by butanol or helium method, peak profile obtained by powder X-ray method, particle size distribution, resonance peak by ⁷ Li-NMR, observation of electron microscope such as transmission type and scanning type, polarization, etc. The material of the carbon material mixture can be specified using microscopic observation or the like.

As the non-graphitic carbon material, a non-graphitizable carbon material (hard carbon) corresponding to a non-graphitic carbon material having a true density (ρ _Bt ) of 1.52 g / cm ³ or more and 1.70 g / cm ³ can be used. Two or more kinds of non-graphitic carbon materials included in the true density (ρ _Bt ) range may be selected and mixed for use.

Non-graphitic carbon material, use a true density ([rho _Bt) is graphitizable carbon material corresponding to the non-graphitic carbon material of greater than 2.15 g / cm ³ than 1.70 g / cm ³ (soft carbon) it can. Two or more kinds of non-graphitic carbon materials included in the true density (ρ _Bt ) range may be selected and mixed for use.

  In the present invention, when the non-graphitic carbon material and the graphite material are mixed, as described above, the non-graphitizable carbon material has a defect that the energy density is not sufficient, and the graphite material is inferior in cycle characteristics. Therefore, it is preferable to consider the mixing ratio so that both the energy density and the cycle characteristics are good. It is preferable to mix the non-graphitizable carbon material at 20 to 80% by mass and the graphite material at 80 to 20% by mass. More preferably, the former is 30 to 70% by mass and the latter is 70 to 30% by mass, and further preferably the former is 40 to 60% by mass and the latter is 60 to 40% by mass.

  In the present invention, when the non-graphitizable carbon material and the graphitic material are mixed, as described above, the graphitizable carbon material has a potential change that inclines in a 50% charged state, but the energy density is not sufficient. The graphite material has a drawback that a high energy density can be obtained but the input / output characteristics are inferior. Therefore, it is preferable to consider the mixing ratio so that both the input characteristics and the energy density are good. It is preferable to mix the easily graphitizable carbon material at 20 to 80% by mass and the graphite material at 80 to 20% by mass. More preferably, the former is 30 to 70% by mass and the latter is 70 to 30% by mass, and further preferably the former is 40 to 60% by mass and the latter is 60 to 40% by mass.

(True density ratio)
For the carbon material mixture of the present invention, the ratio of ρ _Bt to ρ _He (ρ _He / ρ _Bt ) reflects the number of pores large enough to allow butanol to enter but not helium. Such fine pores are considered to be highly involved in moisture absorption in the atmosphere. When the true density ratio is large, the hygroscopicity is excessively increased and the storage stability is liable to be impaired, so that it is preferably 1.30 or less, and more preferably 1.25 or less. The true density ratio of the carbon material mixture of the present invention can be obtained by adding the true density of the carbon material to be mixed according to the mix ratio.

(Specific surface area)
The specific surface area (SSA) obtained by the BET method for nitrogen adsorption of the carbon material mixture of the present invention reflects the amount of voids to which nitrogen gas molecules can enter. If the specific surface area is too small, the input characteristics of the battery tend to be small. Therefore, the carbon material mixture of the present invention is preferably 3.5 m ² / g or more. More preferably, it is 4.0 m ² / g or more. If it is excessive, the irreversible capacity of the obtained battery tends to increase, so it is preferable that it be 40 m ² / g or less. Preferably, it is 30 m ² / g or less.

(Atomic ratio of hydrogen / carbon (H / C))
Regarding the non-graphitic carbon material in the present invention, H / C is measured by elemental analysis of hydrogen atoms and carbon atoms. As the degree of carbonization increases, the hydrogen content of the carbonaceous material decreases, so H / C tends to decrease, which is effective as an index representing the degree of carbonization. H / C of the non-graphitic carbon material in the present invention is preferably 0.10 or less. More preferably, it is 0.08 or less, More preferably, it is 0.05 or less. If the atomic ratio H / C exceeds 0.10, there are many functional groups in the carbonaceous material, and the irreversible capacity may increase due to reaction with lithium, which is not preferable.

(Average layer surface spacing d ₀₀₂ , crystallite thickness L _{c (002)} )
The average layer spacing d ₀₀₂ of the (002) plane of the carbonaceous material is determined by the X-ray diffraction method, but shows a smaller value as the crystal integrity is higher, and the value tends to increase as the structure is disturbed. It is effective as an index indicating the structure of carbon. In the present invention, it is preferable that the graphite material in the present invention has an average layer spacing d _{002 of} (002) plane of 0.347 nm or less because the crystallinity is increased and the energy density per volume is improved. As the non-graphitizable carbon material in the present invention, a non-graphitizable carbon material having an average layer surface spacing of 0.365 nm to 0.390 nm may be used. In this case, if d ₀₀₂ is less than 0.365 nm, the charge / discharge cycle characteristics tend to deteriorate, and if it exceeds 0.390 nm, the irreversible capacity increases, which is not preferable. In addition, as the non-graphitizable carbon material in the present invention, an easily graphitizable carbon material having an average layer surface distance d ₀₀₂ of 0.340 nm or more and 0.375 nm or less may be used. In this case, if d ₀₀₂ is less than 0.340 nm, the input / output characteristics deteriorate, and if d ₀₀₂ exceeds 0.375 nm, the irreversible capacity tends to increase.
When the crystallite thickness L _{c (002) in} the c-axis direction exceeds 15 nm, the non-graphitic carbon material in the present invention is liable to collapse and electrolytic solution decomposition due to repeated charge and discharge, which is not preferable for cycle characteristics.

(Average particle diameter ( _Dv50 ))
Since the particle surface area increases as the average particle diameter (D _v50 ) of the non-graphitic carbon material in the present invention is smaller, the reactivity increases and the electrode resistance decreases, so that the input characteristics are improved. However, if the average particle size is too small, the reactivity is excessively increased and the irreversible capacity tends to increase. On the other hand, if the particles are too small, the amount of binder necessary to form an electrode increases and the resistance of the electrode increases. On the other hand, when the average particle size is increased, it is difficult to apply a thin electrode, and further, the lithium free diffusion process in the particles is increased, so that rapid charge / discharge is difficult. For this reason, it is preferable that average particle diameter _DV50 (namely, particle diameter from which a cumulative volume becomes 50%) is 1-8 micrometers, More preferably, it is 2-6 micrometers or less.

As an index of particle size _{distribution, (D v90 -D v10) / D} v50 can be used, the non-graphitic carbon material in the present invention _{(D v90 -D v10) / D} v50 are points to provide a broad particle size distribution 1.4 or more, and more preferably 1.6 or more. When (D _V90 -D _V10 ) / D _{V50 of the} non-graphitic carbon material is 1.4 or more, dense packing is possible, so that the amount of active material per volume is high and energy per volume is high. The density can be increased. However, since excessively to a broad particle size distribution takes time of pulverization and _{classification,} it is preferable upper limit of _{(D v90 -D v10) / D} v50 is 3 or less.

The ratio of the average particle diameter (D _v50 ) of the non-graphitic carbon material and the average particle diameter (D _v50 ) of the graphite material in the present invention is preferably 1.5 times or more. When the ratio of the particle diameters is 1.5 times or more, small particles can enter the gaps formed by the large particles, so that the active material filling rate can be increased and the electrode density can be increased. Even when the particle diameter of the non-graphitic carbon material is larger or the particle diameter of the graphite material is larger, the same effect can be obtained. More preferably, it is 2.0 times or more, More preferably, it is 2.5 times or more.

  In the present invention, in order to improve the input / output characteristics, although not particularly limited, it is effective to reduce the maximum particle size. If the maximum particle size is excessive, the amount of carbonaceous powder having a small particle size that contributes to improvement of input / output characteristics tends to be insufficient. In order to form a thin and smooth active material layer, the maximum particle size is preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 16 μm or less. Such adjustment of the maximum particle size may be performed by classification after pulverization in the production process.

  In the present invention, in order to improve input / output characteristics, although not particularly limited, it is effective to make the active material layer of the negative electrode thin. The above carbon material mixture can be closely packed, but if so, the voids formed between the carbonaceous powders of the negative electrode are reduced, and the movement of lithium in the electrolytic solution is suppressed, affecting the output characteristics. However, when the active material layer of the negative electrode is thin, the process of lithium ions is shortened, and as a result, the merit of increasing the capacity per volume is easily surpassed compared to the demerit that the migration of lithium due to close packing is suppressed. . From the viewpoint of forming such a thin and smooth active material layer, it is preferable that a large amount of particles having a large particle size is not contained, and specifically, the amount of particles having a particle size of 30 μm or more is 1% by volume or less. Is preferable, more preferably 0.5% by volume or less, and most preferably 0% by volume. Such adjustment of the particle size distribution may be performed by classification after pulverization in the production process.

(Discharge capacity, input value)
According to the negative electrode material of the present invention, a negative electrode having a large discharge capacity and a high Coulomb efficiency expressed by a ratio of charge capacity / discharge capacity can be obtained. Moreover, according to the negative electrode material of the present invention, a negative electrode having a high energy density and a high Coulomb efficiency expressed by a charge capacity / discharge capacity ratio can be obtained. In addition, a negative electrode having a large input and output at 50% charge, which is a practical charge region, and a small electrical resistance of the electrode can be obtained. From the viewpoint of driving range and the charging frequency of the motor vehicle, as the discharge capacity, is preferably 210 mAh / cm ³ or more, more preferably 230 mAh / cm ³ or more. Furthermore, it is preferably 250 mAh / cm ³ or more, more preferably 270 mAh / cm ³ or more. The input value at the time of 50% charging is preferably 10 W / cm ³ or more, more preferably 13 W / cm ³ or more, and further preferably 15 W / cm ³ or more. The cruising distance per charge is extended, which leads to a reduction in in-vehicle space, contributing to improved fuel efficiency.

(Hygroscopic)
The moisture absorption amount after storage for 100 hours in a 25 ° C. 50% RH air atmosphere is preferably 1.0 wt% or less, more preferably 0.75 wt% or less, 0.70 wt% or less, 0.30 wt%,. 18 wt% or less.

(Capacity ratio)
The ratio between the positive electrode capacity and the negative electrode capacity (hereinafter also referred to as “capacity ratio”) is an index indicating the degree of margin of the negative electrode capacity with respect to the positive electrode capacity. The negative electrode material for a non-aqueous electrolyte secondary battery according to the present invention preferably has a certain range in the negative electrode capacity of the secondary battery. For example, when battery design is performed based on the negative electrode capacity by 50 cc CCCV charging, non-graphitic carbon has a certain capacity in the voltage range of 0 to 50 mV, so that it contains non-graphitic carbon. Thus, it is possible to design the negative electrode capacity with a margin relative to the positive electrode capacity. When there is a margin in this negative electrode capacity, the proportion of empty portions that are not used in the Li ion storage sites of the negative electrode active material increases, so that the expansion of the negative electrode active material can be suppressed during charging. Therefore, good cycle characteristics are obtained, which is preferable. Furthermore, even when overcharge occurs, Li ions are occluded (charged) in the vacant portion of the Li ion occlusion site, so that precipitation of Li metal can be suppressed. Therefore, good Li metal deposition resistance is obtained, which is preferable. This improvement in Li metal deposition resistance is particularly important in terms of safety in batteries that carry a large current, such as in-vehicle batteries. On the other hand, if the capacity of the negative electrode capacity is too large, the negative electrode capacity becomes excessive, and accordingly, the irreversible capacity (loss) becomes too large, and the Li ion storage site is not used effectively, so the input / output characteristics deteriorate. It is not preferable. Therefore, the capacity ratio between the positive electrode and the negative electrode is preferably 0.50 to 0.90. More preferably, for example, the non-graphitizable carbon material is 0.50 to 0.85, and the graphitizable carbon material is 0.60 to 0.87.

(Method for producing non-graphitic carbonaceous material)
The negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but based on a manufacturing method similar to the conventional negative electrode material for a non-aqueous electrolyte secondary battery made of a carbonaceous material, firing conditions and grinding conditions It can manufacture favorably by controlling. Specifically, it is as follows.

(Carbon precursor)
The non-graphitic carbonaceous material in the present invention is produced from a carbon precursor. Examples of the carbon precursor include petroleum pitch or tar, coal pitch or tar, thermoplastic resin, or thermosetting resin. In addition, as the thermoplastic resin, polyacetal, polyacrylonitrile, styrene / divinylbenzene copolymer, polyimide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyarylate, polysulfone, polyphenylene sulfide, fluororesin, polyamideimide, or polyether Mention may be made of ether ketones. Furthermore, examples of the thermosetting resin include phenol resin, amino resin, unsaturated polyester resin, diallyl phthalate resin, alkyd resin, epoxy resin, and urethane resin.
In the present specification, the “carbon precursor” means a carbonaceous material from an untreated carbonaceous material stage to a pre-stage of a carbonaceous material for a nonaqueous electrolyte secondary battery finally obtained. That is, it means all the carbonaceous matter that has not finished the final process.
In the present specification, the “carbon precursor that is not meltable with respect to heat” means a resin that does not melt by pre-baking or main baking. That is, in the case of petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin, it means a carbonaceous precursor that has been subjected to an infusibilization treatment described below. On the other hand, since the thermosetting resin does not melt even if pre-baking or main baking is performed as it is, no infusibilization treatment is required.

  When the non-graphitizable carbonaceous material in the present invention is a non-graphitizable carbon material, petroleum pitch or tar, coal pitch or tar, or thermoplastic resin is infusible to heat in the production process. It is necessary to perform the infusibilization process. The infusibilization treatment can be performed by forming a crosslink on the carbon precursor by oxidation. That is, the infusibilization treatment can be performed by a known method in the field of the present invention. For example, it can be performed according to the procedure of infusibilization (oxidation) described later.

(Infusibilization treatment, crosslinking treatment)
When petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin is used as the non-graphitizable carbon precursor, an infusibilization treatment is performed. Moreover, when petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin is used as the graphitizable carbon precursor, a crosslinking treatment is performed. In addition, the graphitizable carbon material does not require a crosslinking treatment (oxidation treatment) in its production, and can be produced without performing the oxidation treatment. The method for infusibilization treatment or the method for crosslinking treatment is not particularly limited, and can be performed using, for example, an oxidizing agent. The oxidizing agent is not particularly limited, but as the gas, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen or the like, or an oxidizing gas such as air is used. Can do. As the liquid, an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide, or a mixture thereof can be used. The oxidation temperature is not particularly limited, but is preferably 120 to 400 ° C, and more preferably 150 to 350 ° C. When the temperature of the non-graphitizable carbon precursor is less than 120 ° C., the crosslinked structure cannot be sufficiently formed, and the particles are fused in the heat treatment step. When the temperature of the graphitizable carbon precursor is lower than 120 ° C., the crosslinked structure cannot be sufficiently formed, and the tendency for the structural regularity to increase increases. Moreover, when temperature exceeds 400 degreeC, a decomposition reaction will increase rather than a crosslinking reaction, and the yield of the carbon material obtained will become low.

  Firing uses a non-graphitic carbon precursor as a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery. When pre-baking and main baking are performed, the temperature may be once lowered after the pre-baking, pulverized, and main baking may be performed.

  The carbonaceous material of the present invention is produced by a step of pulverizing a carbon precursor and a step of firing the carbon precursor.

(Pre-baking process)
The pre-baking step in the present invention is performed by baking the carbon source at 300 ° C. or higher and lower than 900 ° C. Pre-firing removes volatile components such as CO ₂ , CO, CH ₄ , and H ₂ , and tar components, and reduces the generation of these components in the main firing, thereby reducing the burden on the calciner. . When the pre-baking temperature is less than 300 ° C., detarring becomes insufficient, and there is a large amount of tar and gas generated in the main baking process after pulverization, which may adhere to the particle surface. This is not preferable because it cannot be maintained and the battery performance is lowered. The pre-baking temperature is preferably 300 ° C. or higher, more preferably 500 ° C. or higher, and particularly preferably 600 ° C. or higher. On the other hand, when the pre-baking temperature is 900 ° C. or higher, the tar generation temperature region is exceeded, and the energy efficiency to be used is lowered, which is not preferable. Furthermore, the generated tar causes a secondary decomposition reaction, which adheres to the carbon precursor and may cause a decrease in performance, which is not preferable. Also, if the pre-baking temperature is too high, carbonization proceeds and the carbon precursor particles become too hard, and when pulverizing after pre-firing, it becomes difficult to pulverize such as scraping the inside of the pulverizer This is not preferable.
Pre-baking is performed in an inert gas atmosphere, and examples of the inert gas include nitrogen and argon. Pre-baking can also be performed under reduced pressure, for example, 10 kPa or less. The pre-baking time is not particularly limited, but can be performed, for example, for 0.5 to 10 hours, and more preferably 1 to 5 hours.

In the pre-calcination of the carbon precursor having a butanol true density of 1.52 to 1.70 g / cm ³ , the generated tar content is large, and when the temperature is rapidly raised, the particles are foamed or the tar becomes a binder to form particles. Will be fused. Therefore, when pre-baking the carbon precursor having a butanol true density of 1.52 to 1.70 g / cm ³ , it is desirable to make the temperature increase rate of the pre-baking moderate. For example, the rate of temperature rise is preferably 5 ° C./h or more and 300 ° C./h or less, more preferably 10 ° C./h or more and 200 ° C./h or less, and further preferably 20 ° C./h or more and 100 ° C./h or less.

(Crushing process)
The pulverization step in the present invention is performed in order to make the particle size of the carbon precursor uniform. It can also grind | pulverize after carbonization by this baking. As the carbonization reaction proceeds, the carbon precursor becomes hard and it becomes difficult to control the particle size distribution by pulverization. Therefore, the pulverization step is preferably performed after preliminary calcination and before main calcination.
The pulverizer used for pulverization is not particularly limited. For example, a jet mill, a ball mill, a hammer mill, or a rod mill can be used. However, a jet mill having a classification function in that fine powder is generated less. Is preferred. On the other hand, when using a ball mill, a hammer mill, a rod mill or the like, fine powder can be removed by classification after pulverization.
Examples of classification include classification with a sieve, wet classification, and dry classification. Examples of the wet classifier include a classifier using a principle such as gravity classification, inertia classification, hydraulic classification, or centrifugal classification. Examples of the dry classifier include a classifier using the principle of sedimentation classification, mechanical classification, or centrifugal classification.

In the pulverization step, pulverization and classification can be performed using one apparatus. For example, pulverization and classification can be performed using a jet mill having a dry classification function.
Furthermore, an apparatus in which the pulverizer and the classifier are independent can be used. In this case, pulverization and classification can be performed continuously, but pulverization and classification can also be performed discontinuously.
In addition, in order to adjust the particle size distribution of the negative electrode material for a nonaqueous electrolyte secondary battery to be obtained, the particle size is adjusted to be slightly larger in the production stage. This is because the particle size of the carbon precursor is reduced by firing.

(Main firing process)
The main firing step in the present invention can be performed according to a normal main firing procedure, and a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode can be obtained by performing the main firing.
In the case of a non-graphitizable carbon precursor, the temperature for the main firing is 900 to 1600 ° C. If the main calcination temperature is less than 900 ° C., many functional groups remain in the carbonaceous material and the H / C value becomes high, and the irreversible capacity increases due to reaction with lithium. The lower limit of the main firing temperature of the present invention is 900 ° C. or higher, more preferably 1000 ° C. or higher, and further preferably 1100 ° C. or higher. On the other hand, if the main firing temperature exceeds 1600 ° C., the selective orientation of the carbon hexagonal plane increases and the discharge capacity decreases, which is not preferable. The upper limit of the firing temperature of the present invention is 1600 ° C. or less, more preferably 1500 ° C. or less, and further preferably 1450 ° C. or less.
The temperature of the main firing is 900 to 2000 ° C. in the case of an easily graphitizable carbon precursor. If the main calcination temperature is less than 900 ° C., many functional groups remain in the carbonaceous material and the H / C value becomes high, and the irreversible capacity increases due to reaction with lithium. The lower limit of the main calcination temperature of the present invention is 900 ° C. or higher, more preferably 1000 ° C. or higher, and particularly preferably 1100 ° C. or higher. On the other hand, if the main firing temperature exceeds 2000 ° C., the selective orientation of the carbon hexagonal plane increases and the discharge capacity decreases, which is not preferable. The upper limit of the main firing temperature of the present invention is 2000 ° C. or lower, more preferably 1800 ° C. or lower, and further preferably 1600 ° C. or lower.
The main firing is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination. Furthermore, the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. Moreover, this baking can also be performed under reduced pressure, for example, can also be performed at 10 kPa or less. Although the time of this baking is not specifically limited, For example, it can carry out in 0.1 to 10 hours, 0.2 to 8 hours are preferable and 0.4 to 6 hours are more preferable.

(Manufacture of carbonaceous material from tar or pitch)
An example is given and demonstrated below about the manufacturing method of the carbonaceous material of this invention from a tar or a pitch.
First, the tar or pitch was subjected to a crosslinking treatment (infusibilization treatment). The tar or pitch that has been subjected to the crosslinking treatment is carbonized by subsequent firing to become a non-graphitizable carbonaceous material. Tar or pitch includes petroleum tar or pitch replicated during ethylene production, coal tar produced during coal carbonization, heavy component or pitch obtained by distilling off low boiling components of coal tar, tar or pitch obtained by liquefaction of coal Oil or coal tar or pitch can be used. Two or more of these tars and pitches may be mixed.

  Specifically, the infusibilization method or the crosslinking treatment method includes a method using a crosslinking agent or a treatment method using an oxidizing agent such as air. When using a cross-linking agent, a carbon precursor is obtained by adding a cross-linking agent to petroleum tar or pitch, or coal tar or pitch and heating and mixing to proceed with a cross-linking reaction. For example, as the crosslinking agent, polyfunctional vinyl monomers such as divinylbenzene, trivinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, or N, N-methylenebisacrylamide that undergo a crosslinking reaction by radical reaction can be used. The crosslinking reaction with the polyfunctional vinyl monomer is started by adding a radical initiator. As a radical initiator, α, α ′ azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), lauroyl peroxide, cumene hydroperoxide, 1-butyl hydroperoxide, hydrogen peroxide, or the like can be used. .

  Moreover, when a crosslinking reaction is advanced by treating with an oxidizing agent such as air, it is preferable to obtain a carbon precursor by the following method. That is, to a petroleum pitch or coal pitch, a bicyclic to tricyclic aromatic compound having a boiling point of 200 ° C. or higher or a mixture thereof is added as an additive and heated and mixed, and then molded to obtain a pitch molded body. Next, the additive is extracted and removed from the pitch molded body with a solvent having low solubility with respect to pitch and high solubility with respect to the additive to form a porous pitch, which is then oxidized with an oxidizing agent, and then carbon precursor. Get the body. The purpose of the aromatic additive is to extract and remove the additive from the molded pitch molded body to make the molded body porous, to facilitate crosslinking treatment by oxidation, and to obtain a carbonaceous material obtained after carbonization. To make it porous. As said additive, it can select from 1 type, or 2 or more types of mixtures, such as naphthalene, methyl naphthalene, phenyl naphthalene, benzyl naphthalene, methyl anthracene, phenanthrene, or biphenyl, for example. The amount of the aromatic additive added to the pitch is preferably in the range of 30 to 70 parts by mass with respect to 100 parts by mass of the pitch.

  The pitch and additive are mixed in a molten state by heating in order to achieve uniform mixing. The mixture of the pitch and the additive is preferably performed after being formed into particles having a particle diameter of 1 mm or less so that the additive can be easily extracted from the mixture. Molding may be performed in a molten state, or may be performed by a method such as pulverizing the mixture after cooling. Solvents for extracting and removing the additive from the mixture of pitch and additive include aliphatic hydrocarbons such as butane, pentane, hexane, or heptane, mixtures mainly composed of aliphatic hydrocarbons such as naphtha or kerosene, methanol, Aliphatic alcohols such as ethanol, propanol or butanol are preferred. By extracting the additive from the pitch and additive mixture molded body with such a solvent, the additive can be removed from the molded body while maintaining the shape of the molded body. At this time, it is presumed that a through hole for the additive is formed in the molded body, and a pitch molded body having uniform porosity is obtained.

In order to crosslink the resulting porous pitch, it is then oxidized using an oxidizing agent, preferably at a temperature of 120-400 ° C. As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to. It is simple and economical to oxidize at 120 to 400 ° C. and carry out a crosslinking treatment using a gas containing oxygen such as air or a mixed gas of air and other gas such as combustion gas as an oxidizing agent. Is also advantageous. In this case, if the pitch has a low softening point, the pitch melts during oxidation, making it difficult to oxidize. Therefore, the pitch used preferably has a softening point of 150 ° C. or higher.
The non-graphitizable carbon precursor subjected to the crosslinking treatment as described above is pre-fired and then carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere to thereby obtain the carbonaceous material of the present invention. Material can be obtained. The graphitizable carbon precursor subjected to the crosslinking treatment as described above is pre-fired and then carbonized at 900 ° C. to 2000 ° C. in a non-oxidizing gas atmosphere. A carbonaceous material can be obtained.

(Manufacture of carbonaceous material from resin)
A method for producing a carbonaceous material from a resin will be described below with an example.
The carbonaceous material of the present invention can also be obtained by carbonizing at 900 ° C. to 1600 ° C. using a resin as a non-graphitizable carbon precursor. As the resin, a phenol resin, a furan resin, or the like, or a thermosetting resin obtained by partially modifying the functional group of these resins can be used. It can also be obtained by pre-baking the thermosetting resin at a temperature lower than 900 ° C., if necessary, pulverizing, and carbonizing at 900 ° C. to 1600 ° C. Oxidation treatment (infusibilization treatment) may be performed at a temperature of 120 to 400 ° C. as necessary for the purpose of promoting curing of the thermosetting resin, promoting the degree of crosslinking, or improving the carbonization yield.
The carbonaceous material of the present invention can also be obtained by carbonizing at 900 ° C. to 2000 ° C. using a resin as an easily graphitizable carbon precursor. As the resin, a phenol resin, a furan resin, or the like, or a thermosetting resin obtained by partially modifying the functional group of these resins can be used. It can also be obtained by pre-baking the thermosetting resin at a temperature lower than 900 ° C., if necessary, and then pulverizing and carbonizing at 900 ° C. to 2000 ° C. For the purpose of accelerating the curing of the thermosetting resin, accelerating the degree of crosslinking, or improving the carbonization yield, an oxidation treatment may be performed at a temperature of 120 to 400 ° C. as necessary.
As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to.
Furthermore, a carbon precursor obtained by subjecting a thermoplastic resin such as polyacrylonitrile or a styrene / divinylbenzene copolymer to infusibilization treatment can also be used. In these resins, for example, a monomer mixture obtained by mixing a radically polymerizable vinyl monomer and a polymerization initiator is added to an aqueous dispersion medium containing a dispersion stabilizer and suspended by stirring to suspend the monomer mixture into fine droplets. Then, it can be obtained by proceeding radical polymerization by raising the temperature.
The obtained resin can be made into a spherical non-graphitizable carbon precursor by developing a crosslinked structure by infusibilization treatment. Moreover, the obtained resin can be made into a spherical graphitizable carbon precursor by developing a crosslinked structure by a crosslinking treatment.
The oxidation treatment can be performed in a temperature range of 120 to 400 ° C., particularly preferably 170 to 350 ° C., more preferably 220 to 350 ° C. As the oxidizing agent, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing property such as sulfuric acid, nitric acid, hydrogen peroxide water, or the like Liquid can be used.
Thereafter, the carbon precursor that is infusible to heat as described above is pre-fired as necessary, and then pulverized and carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere. The carbonaceous material of the present invention can be obtained. Alternatively, the carbon precursor crosslinked as described above may be pre-baked as necessary, and then pulverized and carbonized at 900 ° C. to 2000 ° C. in a non-oxidizing gas atmosphere. A carbonaceous material can be obtained.
Although the pulverization step can be performed after carbonization, since the carbon precursor becomes hard as the carbonization reaction proceeds, it becomes difficult to control the particle size distribution by pulverization. It is preferable before the main baking later.

(Graphite material)
The graphite material in the present invention is not particularly limited, and examples thereof include natural graphite and artificial graphite.

[2] Negative electrode mixture for nonaqueous electrolyte secondary battery and negative electrode The negative electrode mixture for nonaqueous electrolyte secondary battery of the present invention and the negative electrode for nonaqueous electrolyte secondary battery of the present invention are the nonaqueous electrolyte secondary battery of the present invention. Includes negative electrode materials.

(Manufacture of negative electrode mixture)
The negative electrode mixture of the present invention is prepared by adding a binder (binder) to the carbon material mixture of the present invention, adding an appropriate amount of an appropriate solvent, and kneading.
The binder is not particularly limited as long as it does not react with the electrolytic solution. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), ethylene-propylene-diene copolymer (EPDM), fluororubber (FR), acrylonitrile-butadiene rubber (NBR), sodium polyacrylate, propylene or carboxymethyl cellulose (CMC) can be used. As the solvent, a polar solvent such as N-methylpyrrolidone (NMP) is preferably used in order to dissolve PVDF and form a slurry.

  The water-soluble polymer binder can be used without particular limitation as long as it is soluble in water. Specific examples include cellulosic compounds, polyvinyl alcohol, starch, polyacrylamide, poly (meth) acrylic acid, ethylene-acrylic acid copolymer, ethylene-acrylamide-acrylic acid copolymer, polyethyleneimine, etc. and their derivatives or Salt. Among these, cellulose compounds, polyvinyl alcohol, poly (meth) acrylic acid and derivatives thereof are preferable. Further, it is more preferable to use a carboxymethyl cellulose (CMC) derivative, a polyvinyl alcohol derivative, or a polyacrylate. These can be used alone or in combination of two or more.

The weight average molecular weight of the water-soluble polymer is 10,000 or more, more preferably 15,000 or more, and still more preferably 20,000 or more. If it is less than 10,000, the dispersion stability of the electrode mixture is inferior or it is easy to elute into the electrolytic solution, which is not preferable. The mass average molecular weight of the water-soluble polymer is 6,000,000 or less, more preferably 5,000,000 or less. When the mass average molecular weight exceeds 6,000,000, the solubility in a solvent is lowered, which is not preferable.

  As the binder, a water-insoluble polymer can be used together with a water-soluble polymer. These are dispersed in an aqueous medium to form an emulsion. Preferred water-insoluble polymers include diene polymers, olefin polymers, styrene polymers, (meth) acrylate polymers, amide polymers, imide polymers, ester polymers, and cellulose polymers.

  The other thermoplastic resin used as the binder for the negative electrode is not particularly limited as long as it has a binding effect and has resistance to the non-aqueous electrolyte used and resistance to the electrochemical reaction in the negative electrode. Can be used. Specifically, the two components of the water-soluble polymer and the emulsion are often used. The water-soluble polymer is mainly used as a dispersibility imparting agent or a viscosity modifier, and the emulsion is important for imparting the binding property between the particles and the flexibility of the electrode.

  Among these, preferred examples include homopolymers or copolymers of conjugated diene monomers and (meth) acrylic acid ester monomers, and specific examples thereof include polybutadiene, polyisoprene, polymethyl methacrylate, and polymethyl acrylate. , Polyethyl acrylate, polybutyl acrylate, natural rubber, inprene-isobutylene copolymer, styrene-1,3-butadiene copolymer, styrene-isoprene copolymer, 1,3-butadiene-isoprene-acrylonitrile copolymer, Styrene-1,3-butadiene-isoprene copolymer, 1,3-butadiene-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate copolymer, styrene-acrylonitrile-1,3-butadiene − Taconic acid copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer, styrene-1,3-butadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, acrylonitrile-1, 3-butadiene-methacrylic acid-methyl methacrylate copolymer, styrene-1,3-butadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile Examples include copolymers, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymers, 2-ethylhexyl acrylate-methyl acrylate-acrylic acid-methoxypolyethylene glycol monomethacrylate, and the like. Among these, a polymer (rubber) having rubber elasticity is particularly preferably used. PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), and SBR (styrene butadiene rubber) are also preferred.

  Further, as water-insoluble polymers, those having a polar group such as a carboxyl group, a carbonyloxy group, a hydroxyl group, a nitrile group, a carbonyl group, a sulfonyl group, a sulfoxyl group, and an epoxy group are listed as preferred examples in terms of binding properties. It is done. Particularly preferred examples of the polar group are a carboxyl group, a carbonyloxy group, and a hydroxyl group.

  When the amount of the binder added is too large, the resistance of the obtained electrode is increased, which is not preferable because the internal resistance of the battery is increased and the battery characteristics are deteriorated. Further, if the amount of the binder added is too small, the bonding between the negative electrode material particles and the current collector becomes insufficient, which is not preferable. Although the preferable addition amount of a binder changes also with the kind of binder used, it is 3-13 mass% preferably in a PVDF-type binder, More preferably, it is 3-10 mass%. On the other hand, water-soluble polymer binders often use a mixture of a plurality of binders such as a mixture of SBR and CMC, and the total amount of all binders used is 0.5 to 5 mass. % Is preferable, and more preferably 1 to 4% by mass.

  By using the carbon material mixture of the present invention, an electrode having high conductivity can be produced without particularly adding a conductive auxiliary agent. However, a negative electrode is optionally provided for the purpose of imparting higher conductivity. A conductive additive can be added during preparation of the mixture. As the conductive assistant, conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, etc. can be used, and the amount added varies depending on the type of conductive assistant used, but the amount added is too small. Since the expected conductivity cannot be obtained, it is not preferable, and too much is not preferable because the dispersion in the negative electrode mixture deteriorates. From such a viewpoint, the preferable ratio of the conductive auxiliary agent to be added is 0.5 to 10% by mass (where the amount of the active material (carbonaceous material) + the amount of the binder + the amount of the conductive auxiliary agent = 100% by mass). More preferably, it is 0.5-7 mass%, More preferably, it is 0.5-5 mass%.

(Manufacture of negative electrode)
The negative electrode of the present invention can be produced by applying and drying the negative electrode mixture of the present invention on a current collector plate made of a metal plate or the like, followed by pressure molding. The negative electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. A thicker negative electrode active material layer is preferable for increasing the capacity because fewer current collectors and separators are required. However, a wider electrode area facing the counter electrode is advantageous for improving input / output characteristics, and the active material layer is thicker. Too much is not preferable because the input / output characteristics deteriorate. The thickness of a preferable active material layer (per one surface) is 10 to 80 μm, more preferably 20 to 75 μm, and particularly preferably 20 to 60 μm.

[3] Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention includes the negative electrode for a nonaqueous electrolyte secondary battery of the present invention.

(Manufacture of non-aqueous electrolyte secondary batteries)
When the negative electrode material of the present invention is used to form a negative electrode of a nonaqueous electrolyte secondary battery, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited, and are nonaqueous solvents. Various materials conventionally used or proposed as a secondary battery can be used.

For example, as the positive electrode material, a layered oxide system (represented as LiMO ₂ , where M is a metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Co _y Mo _z O ₂ (where x, y and z represent composition ratios), olivine system (represented by LiMPO ₄ , M is metal: for example, LiFePO _4, etc.), spinel system (represented by LiM ₂ O ₄ , M is a metal: for example, LiMn ₂ O _4, etc. The composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed if necessary, and these positive electrode materials are molded together with an appropriate binder and a carbon material for imparting conductivity to the electrode. The positive electrode is formed by forming a layer on the conductive current collector.

The nonaqueous solvent electrolyte used in combination of these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, vinylene carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1, One or more organic solvents such as 3-dioxolane can be used in combination. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , or LiN (SO ₃ CF ₃ ) ₂ is used. In secondary batteries, the positive electrode layer and the negative electrode layer formed as described above are generally immersed in an electrolytic solution with a liquid-permeable separator made of nonwoven fabric or other porous material facing each other as necessary. It is formed by. As the separator, a non-woven fabric usually used for a secondary battery or a permeable separator made of another porous material can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.
In addition, the nonaqueous electrolyte secondary battery of the present invention preferably has an LUMO value of −1.01 to 1.11 eV calculated using the AM1 (Austin Model 1) calculation method of the semiempirical molecular orbital method for the electrolyte. The additive which is the range of this is included. The nonaqueous electrolyte secondary battery using the negative electrode for a nonaqueous electrolyte secondary battery using the carbonaceous material and additive of the present invention has high dope and dedope capacity and exhibits excellent high temperature cycle characteristics.

  The nonaqueous electrolyte secondary battery of the present invention is suitable as a battery (typically a lithium ion secondary battery for driving a vehicle) mounted on a vehicle such as an automobile.

  The vehicle according to the present invention can be targeted without particular limitation, such as a vehicle commonly known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and at least a power supply device provided with the battery. And an electric drive mechanism driven by power supply from the power supply device, and a control device for controlling the electric drive mechanism. Furthermore, a power generation brake or a regenerative brake may be provided, and a mechanism for converting energy generated by braking into electricity and charging the lithium ion secondary battery may be provided. Since the hybrid vehicle has a particularly low degree of freedom in battery volume, the battery of the present invention is useful.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

The physical properties (ρ _Bt , ρ _He , specific surface area (SSA), average particle size (D _v50 ), hydrogen / carbon atomic ratio (H / C) of the negative electrode material for nonaqueous electrolyte secondary batteries of the present invention are shown below. d ₀₀₂ , L _{c (002),} charging capacity, discharging capacity, irreversible capacity, moisture absorption, input / output value of 50% state of charge, DC resistance value, capacity retention rate, AC resistance value) The physical property values described in this specification including the examples are based on values obtained by the following methods.

(True density by the butanol method (ρ _Bt ))
The true density was measured by a butanol method according to a method defined in JIS R 7212. The mass (m ₁ ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL is accurately measured. Next, the sample is placed flat on the bottom so as to have a thickness of about 10 mm, and its mass (m ₂ ) is accurately measured. Gently add 1-butanol to this to a depth of about 20 mm from the bottom. Next, light vibration is applied to the specific gravity bottle, and it is confirmed that large bubbles are not generated. Then, the bottle is placed in a vacuum desiccator and gradually exhausted to 2.0 to 2.7 kPa. Keep at that pressure for 20 minutes or more, and after the generation of bubbles has stopped, take it out, fill it with 1-butanol, plug it and immerse it in a constant temperature water bath (adjusted to 30 ± 0.03 ° C) for 15 minutes or more. Align the liquid level of 1-butanol with the marked line. Next, this is taken out, the outside is well wiped off and cooled to room temperature, and then the mass (m ₄ ) is accurately measured.

Next, the same specific gravity bottle is filled with only 1-butanol, immersed in a constant temperature bath in the same manner as described above, and after aligning the marked lines, the mass (m ₃ ) is measured. Moreover, distilled water excluding the gas that has been boiled and dissolved immediately before use is collected in a specific gravity bottle, immersed in a constant temperature water bath in the same manner as described above, and the mass (m ₅ ) is measured after aligning the marked lines. ρ _Bt is calculated by the following equation.

このとき、ｄは、水の３０℃における比重（０．９９４６）である。

At this time, d is the specific gravity (0.9946) of water at 30 ° C.

(True density by the helium method (ρ _He ))
Measurement of [rho _{the He} used a Shimadzu dry automatic densimeter Accupyc II1340. The sample was previously dried at 200 ° C. for 5 hours or more and then measured. Using a 10 cm ³ cell, a 1 g sample was placed in the cell, and the measurement was performed at an ambient temperature of 23 ° C. Purge number is 10 times, with the average of 5 times was confirmed to agree to within 0.5% by volume value repeatedly measured (n = 5), and a [rho _{the He.}

  The measuring device has a sample chamber and an expansion chamber, and the sample chamber has a pressure gauge for measuring the pressure in the chamber. The sample chamber and the expansion chamber are connected by a connecting pipe having a valve. A helium gas introduction pipe having a stop valve is connected to the sample chamber, and a helium gas discharge pipe having a stop valve is connected to the expansion chamber.

Specifically, the measurement was performed as follows.
The volume of the sample chamber (V _CELL ) and the volume of the expansion chamber (V _EXP ) are measured in advance using a calibration sphere with a known volume. The sample is placed in the sample chamber, fills the system with helium, the system pressure at that time and P _a. Then closing the valve, is increased to a pressure P ₁ added sample chamber only helium gas. After that, when the valve is opened and the expansion chamber and the sample chamber are connected, the system pressure decreases to P ₂ due to expansion.
At this time, the volume of the sample (V _SAMP ) is calculated by the following equation.

したがって、試料の質量をＷ_ＳＡＭＰとすると密度は

Therefore, if the sample mass is W _SAMP , the density is

となる。

It becomes.

(Specific surface area by nitrogen adsorption (SSA))
An approximate expression derived from the BET expression is described below.

上記の近似式を用いて、液体窒素温度における、窒素吸着による１点法（相対圧力ｘ＝０．２）によりｖ_ｍを求め、次式により試料の比表面積を計算した。

Using the above approximate expression, at liquid nitrogen temperature, 1-point method by nitrogen adsorption seek v _m by (relative pressure x = 0.2), was calculated a specific surface area of the sample by the following equation.

このとき、ｖ_ｍは試料表面に単分子層を形成するに必要な吸着量（ｃｍ^３／ｇ）、ｖは実測される吸着量（ｃｍ^３／ｇ）、ｘは相対圧力である。

In this case, _{v m} is the adsorption amount necessary for forming a monomolecular layer on the surface of the sample ^(cm 3 / g), v the adsorption amount of the measured ^(cm 3 / g), x is a relative pressure.

  Specifically, using “Flow Sorb II2300” manufactured by MICROMERITICS, the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured as follows. A carbonaceous material pulverized to a particle size of about 5 to 50 μm is filled in a sample tube, and while flowing a mixed gas of helium: nitrogen = 80: 20, the sample tube is cooled to −196 ° C. to adsorb nitrogen to the carbonaceous material. Let The sample tube is then returned to room temperature. At this time, the amount of nitrogen desorbed from the sample was measured with a thermal conductivity detector, and the amount of adsorbed gas v was obtained.

(Atomic ratio of hydrogen / carbon (H / C))
Measurement was performed in accordance with the method defined in JIS M8819. The mass ratio of hydrogen and carbon in the sample obtained by elemental analysis using a CHN analyzer (Perkin-elmer 2400II) was divided by the mass number of each element to obtain the hydrogen / carbon atom ratio.

(Average layer spacing (d ₀₀₂ ) and crystallite thickness (L _{c (002)} ) by X-ray diffraction method)
The carbonaceous material powder was filled in the sample holder and measured by a symmetrical reflection method using X'Pert PRO manufactured by PANalytical. The scanning range was 8 <2θ <50 °, and the applied current / applied voltage was 45 kV / 40 mA. An X-ray diffraction pattern was obtained using a CuKα ray (λ = 1.5418Å) monochromated by a Ni filter as a radiation source. . The diffraction pattern was corrected using the diffraction line on the (111) plane of the high-purity silicon powder for the standard substance without correcting the Lorentz changing factor, absorption factor, atomic scattering factor, and the like. D ₀₀₂ was calculated according to the Bragg formula.

Further, the crystallite thickness L _{c (002)} in the c-axis direction was calculated by substituting the following values into Scherrer's equation.
K: Form factor (0.9),
λ: wavelength of X-ray (CuK _α = 0.15418 nm),
θ: diffraction angle,
β: FWHM of the 002 diffraction peak (2θ corresponding to half the intensity of the peak)

(Average particle diameter ( _Dv50 ), particle size distribution by laser diffraction method)
Three drops of a dispersing agent (cationic surfactant “SN Wet 366” (manufactured by San Nopco)) are added to about 0.01 g of the sample, and the dispersing agent is acclimated to the sample. Next, after adding pure water and dispersing with ultrasonic waves, a particle size distribution in the range of particle diameter of 0.02 to 1500 μm was determined with a particle size distribution measuring instrument (“Microtrac MT3300EX” manufactured by Nikkiso Co., Ltd.). From the obtained particle size distribution, the particle diameter at which the cumulative (integrated) volume particle diameter becomes 50% was _{defined as the} volume average particle diameter D _v50 (μm). Further, the particle diameters at which the volume particle diameters were 90% and 10%, respectively, were _defined as D _v90 (μm) and D _v10 (μm). _Then, it subtracted _{D v10} from _{D v90,} a value obtained by dividing _{D v50} the _{((D v90 -D v10) /} D v50) as an indicator of the particle size distribution.
Further, the particle diameter at which the cumulative (integrated) volume particle diameter becomes 100% was defined as the maximum particle diameter.

(Moisture absorption)
Before the measurement, the negative electrode material was vacuum-dried at 200 ° C. for 12 hours, and then 1 g of this negative electrode material was spread on a petri dish having a diameter of 8.5 cm and a height of 1.5 cm so as to be as thin as possible. After leaving in a constant temperature and humidity chamber controlled at a constant temperature of 25 ° C. and a humidity of 50% for 100 hours, the petri dish is taken out of the constant temperature and humidity chamber and the Karl Fischer moisture meter (Mitsubishi Chemical Analytech / CA-200). The moisture absorption was measured using The temperature of the vaporization chamber (VA-200) was 200 ° C.

(Active material electrode performance and battery performance test)
Non-graphitic carbonaceous materials a-1 to a-5 and b-1 to b-7 obtained in the production examples of non-graphitic carbon materials, carbonaceous materials a- obtained in the production examples of graphitic carbon materials 6 to a-7 are used to prepare the carbon material mixture of the example and the comparative carbon material mixture of the comparative example, and the following operations (a) to (e) are performed to form the negative electrode and the nonaqueous electrolyte secondary battery. And the electrode performance was evaluated.

(A) Production of negative electrode 95 parts by mass of the carbon material mixture, 2 parts by mass of a conductive additive (Denka Black manufactured by Denki Kagaku Kogyo), 2 parts by mass of SBR (molecular weight 250,000 to 300,000), CMC (manufactured by Daiichi Kogyo Seiyaku) A pure negative electrode mixture was prepared by adding ultrapure water to 1 part by mass of (Serogen 4H), and uniformly applied onto the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain an electrode. The amount of carbonaceous material in the electrode was adjusted to about 10 mg.
When polyvinylidene fluoride is used as the binder, the composition of the electrode is 90 parts by mass of the above carbon material mixture, 2 parts by mass of a conductive additive (Denka Black manufactured by Denki Kagaku Kogyo), polyvinylidene fluoride (manufactured by Kureha Corporation). “KF # 9100”) was changed to 8 parts by mass to prepare a negative electrode. After drying this, it was punched out into a disk shape having a diameter of 15 mm from a copper foil, and this was pressed to obtain an electrode.

(B) Preparation of test battery The carbon material mixture of the present invention is suitable for constituting the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (de-doping amount) and irreversible capacity (non-reduction capacity) of the battery active material. In order to accurately evaluate (de-doping amount) without being affected by variations in the performance of the counter electrode, a lithium secondary battery is constructed using the electrode obtained above with lithium metal having stable characteristics as the counter electrode. The characteristics were evaluated.

  The lithium electrode was prepared in a glove box in an Ar atmosphere. A 16 mm diameter stainless steel mesh disk was spot welded to the outer lid of a CR2016 size coin-shaped battery can beforehand, and then a 0.8 mm thick metal lithium sheet was punched into a 15 mm diameter disk shape. To be an electrode (counter electrode).

A pair of electrodes manufactured in this manner was used, and an electrolyte solution was obtained by adding LiPF ₆ at a rate of 1.2 mol / L to a mixed solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 3: 7. Using a microporous membrane made of borosilicate glass fiber with a diameter of 17 mm as a separator, and using a polyethylene gasket, a CR2016 size coin-type non-aqueous electrolyte lithium secondary battery in an Ar glove box Assembled.

(C) Measurement of battery capacity About the lithium secondary battery of the said structure, the charge / discharge test was done using the charge / discharge test apparatus ("TOSCAT" by Toyo System). Lithium doping reaction on the carbon electrode was performed by the constant current constant voltage method, and dedoping reaction was performed by the constant current method. Here, in a battery using a lithium chalcogen compound for the positive electrode, the lithium doping reaction to the carbon electrode is “charging”, and the lithium is used for the counter electrode as in the test battery prepared in (a) to (b) of the present invention. In a battery using a metal, the doping reaction to the carbon electrode is referred to as “discharge”, and the naming of the lithium doping reaction to the same carbon electrode differs depending on the counter electrode used. Therefore, for the sake of convenience, the lithium doping reaction on the carbon electrode will be described as “charging”. Conversely, “discharge” is a charging reaction in the test batteries prepared in (a) to (b), but it is described as “discharge” for convenience because it is a dedoping reaction of lithium from a carbonaceous material.
The charging method employed here is a constant current constant voltage method. Specifically, constant current charging was performed at a current density of 0.5 mA / cm ² until the terminal (battery) voltage reached 50 mV, and reached 50 mV. Charging was performed while maintaining a constant voltage at the time, and charging was continued until the current value reached 20 μA. The amount of electricity supplied at this time was defined as the charge capacity, and the charge capacity per volume was shown in units of mAh / cm ³ divided by the volume of the carbon material mixture electrode (excluding the volume of the current collector).
After completion of charging, the battery circuit was opened for 30 minutes and then discharged. The discharge was a constant current discharge at 0.5 mA / cm ² and the final voltage was 1.5V. The amount of electricity discharged at this time was defined as the discharge capacity, and the discharge capacity per volume was shown in units of mAh / cm ³ divided by the volume of the carbon material mixture electrode (excluding the volume of the current collector).
Next, the irreversible capacity was determined as the difference between the charge capacity and the discharge capacity. Coulomb efficiency (%) was obtained by multiplying the value obtained by dividing the discharge capacity by the charge capacity by 100. This is a value indicating how effectively the active material has been used. Characteristic measurements were performed at 25 ° C. For the test batteries prepared using the same sample, the charge / discharge capacity and the irreversible capacity were determined by averaging three measurement values (n = 3).

(D) Production of battery for input / output characteristics test and cycle characteristics test The positive electrode was 94 parts by mass of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (Cellcore MX6 manufactured by umicore), carbon black (Supercal manufactured by TIMCAL). NMP was added to 3 parts by mass and 3 parts by mass of polyvinylidene fluoride (Kureha KF # 7200) to form a paste, which was uniformly applied on the aluminum foil. After drying, the coated electrode was punched onto a disk having a diameter of 14 mm and pressed to obtain an electrode. The amount of LiNi _1/3 Co _1/3 Mn _1/3 O _{2 in} the electrode was adjusted to about 15 mg.
For the negative electrode, a negative electrode was produced in the same procedure as in the above (a) except that the amount of the carbonaceous material in the negative electrode was adjusted so as to be 95% of the charge capacity of the negative electrode active material. Note that the capacity of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was calculated as 165 mAh / g, and 1C (C represents a time rate) was 2.475 mA.
Using the pair of electrodes prepared in this manner, an electrolytic solution obtained by adding LiPF ₆ at a ratio of 1.2 mol / L to a mixed solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 3: 7 was used. A CR2032 size coin-type non-aqueous electrolyte lithium secondary battery is used in an Ar glove box using a borosilicate glass fiber microporous membrane having a diameter of 17 mm as a separator and a polyethylene gasket. Assembled.

(E) Input / output characteristic test and DC resistance test in 50% state of charge For the non-aqueous electrolyte secondary battery having the configuration of (d) above, a battery test was performed using a charge / discharge tester (“TOSCAT” manufactured by Toyo System). went. After aging first, an input / output test and a direct current resistance test were started in a 50% state of charge. Aging procedures (e-1) to (e-3) are shown below.

Aging procedure (e-1)
Using the constant current constant voltage method, constant current charging is performed at a current value of C / 10 until the battery voltage reaches 4.2 V, and then the battery voltage is maintained at 4.2 V (held at a constant voltage). While) the current value was attenuated and charging was continued until the current value became C / 100 or less. After completion of charging, the battery circuit was opened for 30 minutes.

Aging procedure (e-2)
The battery was discharged at a constant current value of C / 10 until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes.

Aging procedure (e-3)
Aging procedures (e-1) to (e-2) were repeated two more times.

  After the end of aging, constant current charging is performed at a current value of 1 C until the battery voltage reaches 4.2 V using the constant current constant voltage method, and then the battery voltage is maintained at 4.2 V (to a constant voltage). Charging was continued until the current value was reduced to C / 100 or less while the current value was attenuated. Discharging was performed once at a current value of 1C until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes. Thereafter, discharging was performed at a constant current value of 1 C until the battery voltage reached 2.75 V, and the discharging capacity at this time was set to 100% discharging capacity.

  Input / output test and DC resistance value test are Matsushita Battery Industry 2005-2006 NEDO report on lithium battery technology development for fuel cell vehicles Automotive lithium battery technology development (high-input / long-life lithium ion battery technology) Development) 3) -1. The input / output test and DC resistance value test procedures (e-4) to (e-11) are shown below.

Input / output test and DC resistance test procedure (e-4)
In a charged state of 50% with respect to the discharge capacity, discharging was performed at a current value of 1 C for 10 seconds, and then the battery circuit was opened for 10 minutes.

Input / output test and DC resistance test procedure (e-5)
After charging at a current value of 1 C for 10 seconds, the battery circuit was opened for 10 minutes.

Input / output test and DC resistance test procedure (e-6)
Change the charge / discharge current values in the input / output test procedures (e-4) and (e-5) to 2C and 3C, and perform the input / output test procedures (e-4) to (e-5) in the same manner. It was.

Input / output test and DC resistance test procedure (e-7)
On the charge side, the voltage at 10 seconds was plotted against each current value, and an approximate straight line was obtained by the method of least squares. By extrapolating this approximate straight line, the current value when the upper limit voltage on the charging side was 4.2 V was calculated.

Input / output test and DC resistance test procedure (e-8)
The product of the obtained current value (A) and the upper limit voltage (V) is the input value (W), and the unit is W / cm ³ divided by the volume of the positive electrode and the negative electrode (excluding the volume of both current collectors). As shown, input values per volume are shown.

Input / output test and DC resistance test procedure (e-9)
Similarly, the voltage at 10 seconds on the discharge side was plotted against each current value, and an approximate straight line was obtained by the least square method. By extrapolating this approximate straight line, the current value when the lower limit voltage on the discharge side was 2.75 V was calculated.

Input / output test and DC resistance test procedure (e-10)
The product of the obtained current value (A) and the lower limit voltage (V) is the output value (W), and the unit is W / cm ³ divided by the volume of the positive electrode and the negative electrode (excluding the volume of both current collectors). The output value per volume is shown.

Input / output test and DC resistance test procedure (e-11)
On the discharge side, the voltage difference from the current application stop to 10 minutes after the current application was plotted against each current value, and an approximate straight line was obtained by the least square method. The slope of this approximate straight line was defined as the DC resistance value (Ω).

(F) Evaluation of cycle characteristics In a combination battery with a LiNi _1/3 Co _1/3 Mn _1/3 O ₂ positive electrode, the discharge amount after 700 cycles at 50 ° C. is defined as the capacity retention rate (%) with respect to the initial discharge amount. Asked.

The evaluation battery was produced in the same procedure as in the above (d).
About the nonaqueous electrolyte secondary battery of the said (d) structure, the battery test was done using the charging / discharging tester ("TOSCAT" by Toyo System). After aging first, a cycle characteristic test was started. Aging procedures (f-1) to (f-3) are shown below.

Aging procedure (f-1)
Using the constant current constant voltage method, constant current charging is performed at a current value of C / 20 until the battery voltage reaches 4.1 V, and then the battery voltage is maintained at 4.1 V (held at a constant voltage). While) the current value was attenuated and charging was continued until the current value became C / 100 or less. After completion of charging, the battery circuit was opened for 30 minutes.

Aging procedure (f-2)
The battery was discharged at a constant current value of C / 20 until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes.

Aging procedure (f-3)
The upper limit battery voltage of the aging procedure (f-1) is changed to 4.2 V, the current values of (f-1) and (f-2) are changed from C / 20 to C / 5, and (f-1) to (F-2) was repeated twice.

After the end of aging, constant current charging is performed at a current value of 2 C until the battery voltage reaches 4.2 V using the constant current constant voltage method, and then the battery voltage is maintained at 4.2 V (to a constant voltage). Charging was continued until the current value was reduced to C / 100 or less while the current value was attenuated. Discharging was performed once at a current value of 2C until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes. Thereafter, discharging was performed at a constant current value of 2 C until the battery voltage reached 2.75 V, and the unit was divided into mAh / cm ³ divided by the volume of the positive electrode and the negative electrode (excluding the volume of both current collectors). The discharge capacity was shown. The discharge capacity at this time is defined as the discharge capacity of the first cycle.
This charging / discharging method was repeated 700 cycles at 50 ° C. The discharge capacity at the 700th cycle was divided by the discharge capacity at the first cycle to obtain a capacity retention rate (%).
When the binder for the negative electrode was changed to polyvinylidene fluoride, the discharge capacity at the 300th cycle was divided by the discharge capacity at the first cycle to obtain a capacity retention rate (%).

(G) AC resistance measurement AC resistance measurement was performed during the evaluation of the cycle characteristics of (f) above. The AC resistance value was measured at a measurement current of 100 μA by applying an AC waveform having a measurement frequency of 1 kHz before starting the discharge at the 700th cycle. When the binder for the negative electrode was changed to polyvinylidene fluoride, an AC waveform having a measurement frequency of 1 kHz was applied before the discharge at the 300th cycle, and measurement was performed at a measurement current of 100 μA.

(H) Calculation of Capacity Ratio The ratio between the positive electrode capacity and the negative electrode capacity of the coin-type non-aqueous electrolyte lithium secondary battery produced in (d) above was calculated. As a test battery for evaluation, a coin-type non-aqueous electrolyte lithium secondary battery was produced in the same procedure as in the above (b). This test battery is charged with a constant current at a current density of 0.5 mA / cm ² until the terminal (battery) voltage reaches 0 V. When the voltage reaches 0 V, the battery is charged with a constant voltage, and the current value reaches 20 μA. Charging continued until reached. The charge capacity per mass (negative electrode capacity by CCCV charge at 0 V) was calculated from the amount of electricity supplied at this time.
The positive electrode capacity is the amount (15 mg) and capacity (165 mAh / g) of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ in the electrode of the coin-type non-aqueous electrolyte lithium secondary battery produced in (d) above. ). The negative electrode capacity is adjusted so that the amount of the carbonaceous material in the electrode of the coin-type non-aqueous electrolyte lithium secondary battery prepared in (d) above is 95% of the capacity of the negative electrode active material due to CCCV charging at 50 mV. And the negative electrode capacity by CCCV charging at 0V. The capacity ratio was calculated from the ratio of the two.

As the binder, in addition to the mixture of SBR and CMC dissolved in water, the one obtained by dissolving polyvinylidene fluoride in organic solvent NMP was also measured. NMP is added to 90 parts by mass of the above carbon material mixture, 2 parts by mass of Denka Black (conducting aid manufactured by Denki Kagaku Kogyo), and 8 parts by mass of polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Co., Ltd.) to obtain a paste. It was uniformly applied on the foil. After drying this, it was punched out into a disk shape having a diameter of 15 mm from a copper foil, and this was pressed to obtain an electrode.
The evaluations (a) to (f) were measured in the same manner except that the binder for the negative electrode was changed to polyvinylidene fluoride and the electrode was changed to the above composition.
Tables 1 and 2 show the battery characteristics.

The first embodiment according to the present invention was tested as follows.
(Example of production of non-graphitic carbon material a-1)
A 70 kg petroleum pitch with a softening point of 205 ° C. and an H / C atomic ratio of 0.65 and 30 kg of naphthalene are charged into a 300 liter pressure vessel equipped with a stirring blade and an outlet nozzle, and heated, melted and mixed at 190 ° C. After cooling to 80 to 90 ° C., the inside of the pressure vessel was pressurized with nitrogen gas, and the contents were extruded from the outlet nozzle to obtain a string-like molded body having a diameter of about 500 μm. Subsequently, this string-like molded body was pulverized so that the ratio (L / D) of the diameter (D) to the length (L) was about 1.5, and the obtained crushed material was heated to 93 ° C. The solution was poured into an aqueous solution in which 53% by mass of polyvinyl alcohol (saponification degree 88%) was dissolved, stirred and dispersed, and cooled to obtain a spherical pitch molded body slurry. After most of the water was removed by filtration, naphthalene in the pitch molded body was extracted and removed with n-hexane having a mass about 6 times that of the spherical pitch molded body. The porous spherical pitch obtained in this manner was heated to 270 ° C. while passing through heated air using a fluidized bed, and kept at 270 ° C. for 1 hour to oxidize to obtain a porous spherical oxidized pitch.
Next, the oxidation pitch was raised to 650 ° C. in a nitrogen gas atmosphere (normal pressure) and maintained at 650 ° C. for 1 hour to perform pre-carbonization to obtain a carbon precursor having a volatile content of 2% or less. The obtained carbon precursor was pulverized to adjust the particle size distribution to obtain a powdery carbon precursor having an average particle size of about 10 μm.
60 g of this powdery carbon precursor was deposited on a graphite board, placed in a horizontal tube furnace having a diameter of 300 mm, and heated to 1180 ° C. at a rate of 250 ° C./h while flowing 5 liters of nitrogen gas per minute. Was held for 1 hour to obtain a carbonaceous material a-1 having an average particle diameter of 9 μm.

(Production Example of Non-graphitic Carbon Material a-2)
The average particle diameter of 3.5 μm was the same as in Production Example a-1 of non-graphitic carbon material, except that the oxidation temperature of the porous spherical pitch was 240 ° C., the particle size distribution was adjusted and the pulverized particle diameter was changed to about 4 μm. Of carbonaceous material a-2 was obtained.

(Production Example a-3 of Non-graphitic Carbon Material)
The average particle size is 4.6 μm in the same manner as in the non-graphitic carbon material production example a-1, except that the oxidation temperature of the porous spherical pitch is 230 ° C. and the particle size distribution is adjusted to change the pulverized particle size to about 5 μm. Of carbonaceous material a-3 was obtained.

(Production Example a-4 of Non-graphitic Carbon Material)
The average particle size is 7.3 μm in the same manner as in Production Example a-1 of non-graphitic carbon material, except that the oxidation temperature of the porous spherical pitch is 210 ° C., the particle size distribution is adjusted and the pulverized particle size is changed to about 8 μm. Of carbonaceous material a-4 was obtained.

(Production Example a-5 of Non-graphitic Carbon Material)
The average particle size is 6.4 μm in the same manner as in the non-graphitic carbon material production example a-1, except that the oxidation temperature of the porous spherical pitch is 190 ° C., the particle size distribution is adjusted and the pulverized particle size is changed to about 7 μm. Of carbonaceous material a-5 was obtained.

(Production Example of Graphite Carbon Material a-6)
The particle size distribution of artificial graphite (CMS-G10 manufactured by Shanghai Sugisugi) was adjusted to an average particle size of 10 μm, and a carbonaceous material a-6 was obtained.

(Production Example of Graphite Carbon Material a-7)
The particle size distribution of artificial graphite (CMS-G10 manufactured by Shanghai Sugisugi) was adjusted to an average particle size of 3.5 μm, and a carbonaceous material a-7 was obtained.

(Examples a-1 to a-14)
As shown in Table 3, in Example a-1, a carbon material mixture prepared by mixing 80% by mass of carbonaceous material a-2 and 20% by mass of carbonaceous material a-7 by a planetary kneader is prepared. Then, a test battery using the negative electrode active material was prepared. Also for Examples a-2 to a-14, a carbon material mixture mixed at a ratio as shown in Table 3 was prepared, and a test battery was produced.

(Comparative Examples a-1 to a-4)
As shown in Table 3, Comparative Example a-1 prepared a comparative carbon material mixture in which 40% by mass of carbonaceous material a-1 and 60% by mass of carbonaceous material 4 were mixed by a planetary kneader. A test battery using the negative electrode active material was prepared. For Comparative Examples a-2 to a-4, a comparative carbon material mixture mixed at a ratio as shown in Table 3 was prepared to prepare a test battery.

(Comparative Examples a-5 to a-7)
As shown in Table 5, in Comparative Example a-5 and Comparative Example a-6, the carbon material mixture of Example a-6 was used, and the capacity ratio was 0.45 and 0.91 in the negative electrode. A test battery was prepared by the same procedure as in the above (d) except that the amount of the carbon material was adjusted. Comparative Example a-7 produced a test battery having a capacity ratio of 0.91 in the same procedure using the carbon material mixture of Example a-9.

  Tables 1 to 5 show the carbonaceous materials obtained in the examples and comparative examples, the characteristics of the carbon material mixture, the negative electrodes produced using the carbonaceous materials, and the measurement evaluation results of the battery performance.

For each example and comparative example, true density (ρ _Bt ), true density (ρ _He ), average particle diameter, specific surface area (SSA), moisture absorption, charge / discharge capacity, input / output values of 50% charge state, and DC resistance The value, the capacity retention rate after the cycle test, the volume capacity and the AC resistance value, and the ratio between the positive electrode capacity and the negative electrode capacity were measured.
As shown in the table, since the negative electrode using the comparative carbon material mixture of Comparative Examples a-1 to a-2 does not include the graphite material within the scope of the present invention, the discharge capacity per volume at the time of setting 50 mV is shown. Low and practical energy density per volume was insufficient. In Comparative Example a-3, since the particle diameter was outside the range of the present invention, the input characteristics in the 50% charged state were insufficient. In Comparative Example a-4, since the comparative carbon material mixture was composed of only the graphite material, the capacity retention after the 50 ° C. cycle test was low.
On the other hand, the negative electrode including the carbon material mixtures a-1 to a-14 of Examples a-1 to a-14 in which the non-graphitic carbon and the graphite material according to the present invention are mixed has a volume per 50 mV setting. The discharge capacity is high, the practical energy density per volume is improved, and both the input characteristics and the cycle characteristics are improved.

Regarding the ratio of positive electrode capacity to negative electrode capacity (capacity ratio), as shown in Table 5, Example a-6 and Example a-9 have a capacity ratio in the range of 0.50 to 0.90. There was an appropriate margin for the negative electrode capacity.
On the other hand, Comparative Example a-5 is in a small range where the capacity ratio is less than 0.50, and accordingly, the negative electrode capacity has an excessive margin and the Li storage site is not effectively utilized. Compared with 6, input / output characteristics deteriorated. Comparative Example a-6 and Comparative Example a-7 are in a large range in which the capacity ratio exceeds 0.90, the negative electrode capacity has insufficient margin, and due to the influence of expansion and contraction due to charge / discharge, Example a-6, The cycle characteristics were reduced as compared with Example a-9.

With respect to the second embodiment according to the present invention, tests were conducted as follows.
(Production Example b-1 of Non-graphitic Carbon Material)
A 70 kg petroleum pitch with a softening point of 205 ° C. and an H / C atomic ratio of 0.65 and 30 kg of naphthalene are charged into a 300 liter pressure vessel equipped with a stirring blade and an outlet nozzle, and heated, melted and mixed at 190 ° C. After cooling to 80 to 90 ° C., the inside of the pressure vessel was pressurized with nitrogen gas, and the contents were extruded from the outlet nozzle to obtain a string-like molded body having a diameter of about 500 μm. Subsequently, this string-like molded body was pulverized so that the ratio (L / D) of the diameter (D) to the length (L) was about 1.5, and the obtained crushed material was heated to 93 ° C. The solution was poured into an aqueous solution in which 53% by mass of polyvinyl alcohol (saponification degree 88%) was dissolved, stirred and dispersed, and cooled to obtain a spherical pitch molded body slurry. After most of the water was removed by filtration, naphthalene in the pitch molded body was extracted and removed with n-hexane having a mass about 6 times that of the spherical pitch molded body. The porous spherical pitch thus obtained was heated to 190 ° C. while passing through heated air using a fluidized bed, and was maintained at 190 ° C. for 1 hour for oxidation to obtain a porous spherical oxidized pitch.
Next, the oxidation pitch was raised to 650 ° C. in a nitrogen gas atmosphere (normal pressure) and maintained at 650 ° C. for 1 hour to perform pre-carbonization to obtain a carbon precursor having a volatile content of 2% or less. The obtained carbon precursor was pulverized to adjust the particle size distribution to obtain a powdery carbon precursor having an average particle size of about 7 μm.
60 g of this powdery carbon precursor was deposited on a graphite board, placed in a horizontal tube furnace having a diameter of 300 mm, and heated to 1180 ° C. at a rate of 250 ° C./h while flowing 5 liters of nitrogen gas per minute. For 1 hour to obtain a carbonaceous material b-1 having an average particle size of 6.8 μm.

(Non-graphitic carbon material production example b-2)
A carbonaceous material b- having an average particle size of 7.9 μm was prepared in the same manner as in Production Example b-1, except that the oxidation temperature of the porous spherical pitch was changed to 180 ° C., the particle size distribution was adjusted and the pulverized particle size was changed to about 8 μm. 2 was obtained.

(Non-graphitic carbon material production example b-3)
A carbonaceous material b- having an average particle size of 3.5 μm was prepared in the same manner as in Production Example b-1, except that the oxidation temperature of the porous spherical pitch was changed to 165 ° C. and the particle size distribution was adjusted to change the pulverized particle size to about 4 μm. 3 was obtained.

(Non-graphitic carbon material production example b-4)
A carbonaceous material b- having an average particle size of 3.5 μm was prepared in the same manner as in Production Example b-1, except that the oxidation temperature of the porous spherical pitch was changed to 160 ° C., the particle size distribution was adjusted and the pulverized particle size was changed to about 4 μm. 4 was obtained.

(Non-graphitic carbon material production example b-5)
The carbonaceous material b-5 having an average particle size of 4.5 μm was prepared in the same manner as in Production Example b-1, except that the porous spherical pitch was not oxidized and the particle size distribution was adjusted to change the pulverized particle size to about 5 μm. Got.

(Production Example of Carbonaceous Material b-6)
Non-graphitizable carbon b-6 was obtained in the same manner as in Production Example b-4 except that the pulverized particle size was changed to about 10 μm and the carbonization temperature was changed to 1800 ° C.

(Production Example of Carbonaceous Material b-7)
The particle size distribution of artificial graphite (CMS-G10 manufactured by Shanghai Sugisugi) was adjusted to an average particle size of 10 μm, and a carbonaceous material b-7 was obtained.

(Production Example of Carbonaceous Material b-8)
The particle size distribution of artificial graphite (CMS-G10 manufactured by Shanghai Sugisugi) was adjusted to an average particle size of 3.5 μm, and a carbonaceous material b-8 was obtained.

(Examples b-1 to b-12)
As shown in Table 8, in Example b-1, a carbon material mixture prepared by mixing 50% by mass of carbonaceous material b-4 and 50% by mass of carbonaceous material b-8 was prepared by a planetary kneader. Then, a test battery using the negative electrode active material was prepared. Also in Examples b-2 to b-12, a carbon material mixture mixed at a ratio as shown in Table 8 was prepared, and a test battery was manufactured.

(Comparative Examples b-1 to b-4)
As shown in Table 8, Comparative Example b-1 is a comparative carbon material mixture obtained by mixing 40% by mass of carbonaceous material b-2 and 60% by mass of carbonaceous material b-4 with a planetary kneader. A test battery was prepared and used as a negative electrode active material. For Comparative Examples b-2 to b-4, a comparative carbon material mixture mixed at a ratio as shown in Table 8 was prepared to prepare a test battery. The measurement results are shown in Tables 8-9.

(Comparative Examples b-5 to b-7)
As shown in Table 10, in Comparative Example b-5 and Comparative Example b-6, the carbon material mixture of Example b-1 was used, and the capacity ratio was 0.49 and 0.92. A test battery was prepared by the same procedure as in the above (d) except that the amount of the carbon material was adjusted. In Comparative Example b-7, a test battery having a capacity ratio of 0.92 was produced in the same procedure using the carbon material mixture of Example b-7.

  Tables 5 to 8 show the characteristics of the carbonaceous materials and carbon material mixtures obtained in the examples and comparative examples, the negative electrode produced using the carbonaceous materials, and the measurement evaluation results of battery performance.

For each example and comparative example, true density (ρ _Bt ), true density (ρ _He ), average particle diameter, specific surface area (SSA), moisture absorption, charge / discharge capacity, input / output values of 50% charge state, and DC resistance The value, the capacity retention rate after the cycle test, the volume capacity, the AC resistance value, and the ratio between the positive electrode capacity and the negative electrode capacity were measured.
As shown in Table 7, the negative electrode including the comparative carbon material mixture 1 of Comparative Examples b-1 to b-2 is set to 50 mV because the comparative carbon material mixture is composed of only non-graphitic carbon in the present invention. The discharge capacity per hour was low, and the practical energy density per volume was insufficient. Further, the input characteristics of the 50% charged state were insufficient. In Comparative Example b-3, since the comparative carbon material mixture was composed of only the graphite material in the present invention, the capacity retention after the 50 ° C. cycle test was low. In Comparative Example b-4, since the average particle diameter of non-graphitic carbon contained in the carbon material mixture was large, the input characteristics in the 50% charged state were insufficient.
On the other hand, the negative electrode including the carbon material mixtures b-1 to b-12 of Examples b-1 to b-12 in which the non-graphitic carbon and the graphite material according to the present invention are mixed has a volume per 50 mV setting. The discharge capacity is high, the practical energy density per volume is improved, and both the input characteristics and the cycle characteristics are improved.
Further, as shown in Table 6, since the AC resistance value after the charge / discharge cycle in the example is lower than that in the comparative example, it can be confirmed that the decrease in the input / output value is suppressed even after the charge / discharge cycle. It was.

Regarding the ratio of positive electrode capacity to negative electrode capacity (capacity ratio), as shown in Table 10, Example b-1 and Example b-7 have a capacity ratio in the range of 0.50 to 0.90. There was an appropriate margin for the negative electrode capacity.
On the other hand, Comparative Example b-5 is in a small range where the capacity ratio is less than 0.50, and accordingly, the negative electrode capacity has an excessive margin and the Li storage site is not effectively utilized. Compared with 6, input / output characteristics deteriorated. Comparative Example b-6 and Comparative Example b-7 are in a large range in which the capacity ratio exceeds 0.90, the negative electrode capacity has insufficient margin, and due to the influence of expansion and contraction due to charge / discharge, Example b-1, The cycle characteristics were reduced as compared with Example b-7.

Claims (11)

A negative electrode material for a non-aqueous electrolyte secondary battery comprising a carbon material mixture containing a non-graphitic carbon material and a graphite material as an active material,
The non-graphitic carbon material has an atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis of 0.10 or less, an average particle diameter (D _v50 ) of 1 to ₈ μm,
The graphite material is a negative electrode material for a nonaqueous electrolyte secondary battery having a true density (ρ _Bt ) determined by a butanol method of 2.15 g / cm ³ or more. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-graphitic carbon material has a true density (ρ _Bt ) determined by a butanol method of 1.52 g / cm ³ or more and 1.70 g / cm ³ or less. Negative electrode material. Wherein the non-graphitic carbon material, true density determined by butanol method ([rho _Bt) is a large 2.15 g / cm less than ³ from 1.70 g / cm ^3, a non-aqueous electrolyte secondary battery according to claim 1 Negative electrode material. The ratio of the average particle diameter ( _Dv50 ) of the said non-graphitic carbon material and the average particle diameter ( _Dv50 ) of the said graphite material is 1.5 times or more, The non in any one of Claims 1-3 Negative electrode material for water electrolyte secondary battery. Wherein the non-graphitic carbon _{material, (D v90 -D v10) /} D v50 is 1.4 to 3.0, negative electrode material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4.   The negative electrode material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the carbon material mixture contains 20 to 80% by mass of the non-graphitic carbon material.   A negative electrode mixture for a nonaqueous electrolyte secondary battery comprising the negative electrode material according to claim 1, and further comprising a binder and a solvent.   The negative electrode mixture for a nonaqueous electrolyte secondary battery according to claim 7, comprising a water-soluble polymer binder and water.   A negative electrode for a non-aqueous electrolyte secondary battery obtained with the negative electrode mixture according to claim 7 or 8.   A nonaqueous electrolyte secondary battery comprising the negative electrode according to claim 9, a positive electrode, and an electrolytic solution.   A vehicle equipped with the nonaqueous electrolyte secondary battery according to claim 10.